Solid state relay

ABSTRACT

A solid state relay is formed by mounting a light-emitting element on a light-emitting side lead frame, mounting a light-receiving element or a switching element which operates in response to the light-receiving element and signals from the light-receiving element on a light-receiving side lead frame, arranging these lead frames on the light-emitting side and the light-receiving side to opposite each other, and sealing into one package and is formed by mounting protective element that protects the light-emitting element or the light-receiving element on at least one of the lead frames and arranging the protective element or the protective element and the switching element inside a primary mold resin that seals the light-emitting element and the light-receiving element.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C § 119(a) on PatentApplication No. 2004-059581 filed in Japan on Mar. 3, 2004, the entirecontent of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to solid state relays such as Triacoutput, MOS output or IGBT output, provided in various types ofelectronic devices as switching elements. The present invention relatesespecially to solid state relays best suited for electronic devices suchas power supply devices, household electrical appliances, invertercontrol devices, and the like having circuits that transmit signalswhile electrically isolating input from the output.

2. Description of the Related Art

As shown in FIG. 12, for example, a conventional solid state relay isformed by mounting a light coupling element 91, a switching element 93such as a transistor, a Triac, an IGBT, or a C-MOS switching elementelectrically connected to a light-receiving portion on the lightcoupling element 91, a chip resistor 94 serving as a protective elementon the output side, a chip capacitor 95, and a chip resistor 96 servingas an LED limiting resistor (protective element on the input side)inside the light coupling element 91, on a metallic lead 92 with silverpaste or high temperature solder, for example, and sealing with a blacklight blocking resin 97 in order to protect a chip mounting portion,ensure electrical isolation, and protect the light coupling element 91from external stray light.

Here, in the light coupling element 91, a light path is formed bymounting an LED (used as a light-emitting element) and a photodiode, aphototransistor, a phototriac, a photovoltaic, or the like (used as alight-receiving element) on two opposing lead frames and sealing the twolead frames by a translucent resin, for example.

It should be noted that conventional solid state relays as describedabove are also disclosed in JP 2001-127099A and JP H5-206504A, forexample.

However, in the above-described conventional solid state relay in whichthe light-emitting element, the light-receiving element, the switchingelement, and the protective elements such as the chip resistor and thechip capacitor are mounted, the two lead frames on which thelight-emitting element and the light-receiving element are respectivelymounted are first placed in opposition to each other and sealed withresin through transfer molding, for example, to fabricate the lightcoupling element, and this light coupling element, the switchingelement, and the protective elements are then mounted on a substrate ofstill another lead frame, for example, after which the substrate issealed by resin.

In such a conventional method, the number of resin sealing steps andpart mounting steps increases, and the degree of integration decreases.Thus, there is the problem that the costs rise and also the package sizeof the device becomes large.

The present invention was achieved in view of this situation, and it isan object of the present invention to provide a solid state relay thatallows a simplification of the assembly steps and a miniaturization ofthe device.

SUMMARY OF THE INVENTION

In order to solve the above-described problems, a solid state relay ofthe present invention is formed by mounting a light-emitting element ona light-emitting side lead frame, mounting a light-receiving element ora light-receiving element and a switching element which operates inresponse to signals from the light-receiving element on alight-receiving side lead frame, arranging the light-emitting side andthe light-receiving side lead frames in opposition to each other, andsealing the lead frames into one package, wherein a protective elementthat protects the light-emitting element or the light-receiving elementis mounted on at least one of the lead frames, and the protectiveelement or the protective element and the switching element are arrangedinside a primary mold resin that seals the light-emitting element andthe light-receiving element.

According to this aspect of the invention, because the light-emittingelement, the receiving element, and the protective element or thelight-emitting element, the light-receiving element, the protectiveelement, and the switching element are sealed with the primary moldresin, by carrying out transfer molding once through a translucentresin, it is possible to form a light path and resin seal the elements(the light-emitting element, the light-receiving element, and theprotective element, or the light-emitting element, the light-receivingelement, the protective element, and the switching element) mounted onthe lead frames.

Thus, because a conventional mounting step of a light coupling elementcan be omitted and the number of resin sealing and part mounting stepscan be reduced, the assembly process is simplified and costs can bereduced.

Furthermore, because the solid state relay is manufactured by mountingthe light-emitting element, the light-receiving element, the switchingelement, and the protective element on the two lead frames on thelight-emitting side and the light-receiving side and sealing theseelements with the primary mold resin, it is possible to increase adegree of integration, shrink the package size, and make the devicesmaller.

With the solid state relay of the present invention, it is possible tosimplify the assembly process and the make the device smaller in thismanner.

It should be noted that here the protective elements may be chipresistors and chip capacitors such as a snubber circuit, alight-emitting element limiting resistor or the like.

Furthermore, in the solid state relay of the above-noted configuration,the protective element may be arranged to be separated from opposing thelead frame and any of the light-emitting element, the light-receivingelement, or the light-receiving element and the switching elementmounted on this lead frame.

In this case, because the protective element is separated from the leadframe and any element of the light-emitting element, the light-receivingelement, or the light-receiving element and the switching elementmounted on this lead frame that are opposite the protective element, inthe solid state relay of the above-noted configuration, an electricalisolation distance between the light-receiving element and thelight-emitting element within the device can be ensured. Thus, even if aprotective element that is thicker than the light-emitting element andthe light-receiving element is mounted, the electrical isolationdistance between the light-receiving element and the light-emittingelement within the device can be ensured, for example.

Furthermore, in the solid state relay of the above-noted configuration,the protective element may be mounted opposite a region where the leadframe is not present.

In this case, because neither the lead frame nor any of the otherlight-emitting element, the light-receiving element, or the switchingelement is present in the region opposite the protective element, in thesolid state relay of the above-noted configuration, the electricalisolation distance between the light-receiving element and thelight-emitting element within the device can be ensured.

Furthermore, in the solid state relay of the above-noted configuration,the protective element may be mounted on a side of at least one of thelead frames that is the rear side to the side on which elements aremounted.

In this case, because the protective element is separated from the leadframe and any of the light-emitting element, the light-receivingelement, or the light-receiving element and the switching elementmounted on this lead frame that are opposite the protective element, inthe solid state relay of the above-noted configuration, the electricalisolation distance between the light-receiving element and thelight-emitting element within the device can be ensured.

Furthermore, in the solid state relay of the above-noted configuration,the lead frame opposite the protective element may be bent in thedirection away from the protective element.

In this case, because the protective element is separated from the leadframe and any of the light-emitting element, the light-receivingelement, or the light-receiving element and the switching elementmounted on this lead frame that are opposite the protective element, inthe solid state relay of the above-noted configuration, the electricalisolation distance between the light-receiving element and thelight-emitting element within the device can be ensured.

Furthermore, in the solid state relay of the above-noted configuration,a concave portion for mounting the protective element may be formed inat least one of the lead frames.

In this case, because the protective element is separated from the leadframe and any element of the light-emitting element, the light-receivingelement, or the light-receiving element and the switching elementmounted on this lead frame that are opposite the protective element, inthe solid state relay of the above-noted configuration, the electricalisolation distance between the light-receiving element and thelight-emitting element within the device can be ensured.

Furthermore, in the solid state relay of the above-noted configuration,a floating island portion and a peripheral portion surrounding thisfloating island portion are provided in at least one of the lead frames;a plurality of mounting portions with different gaps between thefloating island portion and the peripheral portion opposing each otherare provided on the floating island portion and the peripheral portionthat opposes this floating island portion; and the protective elementsare mounted to bridge these mounting portions.

In this case, because the gaps between the floating island portion andthe peripheral portion that oppose each other are different among themounting portions, a plurality of the protective elements of differentsize can be mounted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a cutaway portion of a firstembodiment of a solid state relay of the present invention.

FIG. 2 is a cross-sectional view schematically showing the structure ofthe solid state relay shown in FIG. 1.

FIG. 3 is a cross-sectional view schematically showing the structure ofa second embodiment of the solid state relay of the present invention.

FIG. 4 is a cross-sectional view schematically showing the structure ofthe second embodiment of the solid state relay of the present invention.

FIG. 5 is a cross-sectional view schematically showing the structure ofthe second embodiment of the solid state relay of the present invention.

FIG. 6 is a cross-sectional view schematically showing the structure ofthe second embodiment of the solid state relay of the present invention.

FIG. 7 is a cross-sectional view schematically showing the structure ofa modified example of the solid state relay shown in FIG. 6.

FIG. 8 is a top view showing the solid state relay shown in FIG. 7 witha portion of the lead frames omitted.

FIG. 9 is a top view showing the lead frames shown in FIG. 8 afterprotective elements have been mounted.

FIG. 10 is a top view showing a third embodiment of the solid staterelay of the present invention with a portion of the lead framesomitted.

FIG. 11 is a partially enlarged view of the lead frames shown in FIG.10.

FIG. 12 is a diagram showing the internal structure of a conventionalsolid state relay.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are explained below with referenceto the drawings.

First Embodiment

FIG. 1 and FIG. 2 show a first embodiment of a solid state relay 1 witha structure in which a light-emitting side lead frame 2 a and alight-receiving side lead frame 2 b are opposed.

This solid state relay 1 is formed by mounting a light-emitting element3 and a protective element 5 (light-emitting element limiting resistorchip 5 a) on the light-emitting side lead frame 2 a, and mounting alight-receiving element 4, a switching element 6 which operates inresponse to signals from the light-receiving element 4, and a protectiveelement 5 (chip resistor 5 b) on the light-receiving side lead frames 2b, and sealing the lead frames 2 a and 2 b in one package.

The light-emitting side lead frame 2 a and the light-receiving side leadframe 2 b are arranged in opposition to one another. The elements 3, 4,5, and 6 are respectively mounted on the lead frames 2 a and 2 b, afterwhich primary mold resin sealing of the elements is carried out with atranslucent resin 7, and further resin sealing is carried out with ablack light blocking resin 8. Thus, by carrying out a transfer moldingprocess once with the translucent resin 7, the formation of a light pathand resin sealing of the light-emitting element 3, the light-receivingelement 4, the protective elements 5, and the switching element 6 becomepossible, and the conventional step of mounting a light coupling elementcan be omitted.

It should be noted that the arrangement of the protective elements 5 isnot limited to the above-noted arrangement, and it is also possible thatonly the light-emitting element limiting resistor chip 5 a is mounted onthe light-emitting side lead frame 2 a or that only the chip resistor 5b is mounted on the light-receiving side lead frame 2 b, for example.

Second Embodiment

Next, Embodiment 2 of the present invention is explained with referenceto the drawings.

FIG. 3 to FIG. 9 shows the second embodiment of the present invention.

In the solid state relay 1 according to this embodiment, in order toensure an electrical isolation distance between the light-receivingelement and the light-emitting element within the device in the solidstate relay 1 of the configuration according to the first embodiment,the protective elements 5 are arranged to be separated from the opposinglead frame 2 a and the elements (in FIG. 3 to FIG. 9, the light-emittingelement 3) mounted on this lead frame 2 a, and there are the followingvariations, for example.

In the solid state relay 1 shown in FIG. 3, the protective element 5 ismounted on a region on a front side that opposes the light-emitting sidelead frame 2 a of the light-receiving side lead frame 2 b. Furthermore,the light-emitting side lead frame 2 a is not present in the regionopposite the protective element 5 mounted on a region on the front sideof this light-receiving side lead frame 2 b. In this case, because thelight-emitting side lead frame 2 a is not present in the region oppositethe protective element 5, the protective element 5 can be separated fromthe light-emitting side lead frame 2 a and the element (light-emittingelement 3) mounted on this lead frame 2 a. Thus, even if a protectiveelement 5 thicker than, for example, the light-emitting element 3 andthe light-receiving element 4 is mounted, the electrical isolationdistance between the light-receiving element and the light-emittingelement within the device can be ensured, for example.

It should be noted that the arrangement of the protective element 5 andthe shape of the lead frames 2 a and 2 b are not limited to theabove-noted case, and the arrangement of the protective element 5 andthe shape of the lead frames 2 a and 2 b may also be such that theprotective element 5 is mounted on a region on the front side of thelight-emitting side lead frame 2 a, and the light-receiving side leadframe 2 b is not present in the region opposite the protective element5, for example.

In the solid state relay 1 shown in FIG. 4, the protective element 5 ismounted on the back side of the light-receiving side lead frame 2 b,which does not face the light-emitting side lead frame 2 a. In thissolid state relay 1, the protective element 5 can be separated from thelight-emitting side lead frame 2 a and the element (light-emittingelement 3) mounted on this lead frame 2 a. Thus, even if a protectiveelement 5 thicker than the light-emitting element 3 and thelight-receiving element 4 is mounted, the electrical isolation distancebetween the light-receiving element and the light-emitting elementwithin the device can be ensured.

It should be noted that the face on which the protective element 5 ismounted may be the back side of the light-emitting side lead frame 2 a,which does not oppose the light-receiving side lead frame 2 b.

In the solid state relay 1 shown in FIG. 5, the light-emitting side leadframe 2 a that opposes the protective element 5 is bent in the directionaway from the protective element 5. In this case, it is possible tofurther separate the protective element 5 from the light-emitting sidelead frame 2 a by a distance corresponding to a depth ×1 of a bentportion of the light-emitting side lead frame 2 a. Thus, even if aprotective element 5 thicker than that of the light-emitting element 3and the light-receiving element 4 is mounted, the electrical isolationdistance between the light-receiving element and the light-emittingelement within the device can be ensured, for example.

It should be noted that the arrangement of the protective element 5 andthe shape of the lead frames 2 a and 2 b are not limited to theabove-noted case, and the protective element 5 may also be mounted onthe light-emitting side lead frame 2 a, and the light-receiving sidelead frame 2 b that opposes the protective element 5 may be bent in thedirection away from the protective element 5, for example.

In the solid state relay 1 shown in FIG. 6, a concave portion 2 c ontowhich the protective element 5 is mounted is formed in thelight-receiving side lead frame 2 b.

This concave portion 2 c is formed by bending a portion of thelight-receiving side lead frame 2 b in the direction away from thelight-emitting side lead frame 2 a. As a result of mounting theprotective element 5 on the concave portion 2 c, it is possible tofurther separate the protective element 5 from the light emitting sidelead frame 2 a by a distance corresponding to a depth ×2 of the concaveportion 2 c. Thus, even if a protective element 5 thicker than thelight-emitting element 3 and the light-receiving element 4 is mounted,the electrical isolation distance between the light-receiving elementand the light-emitting element within the device can be ensured, forexample.

Furthermore, as shown in FIG. 7 and FIG. 8, it is also possible thatonly those portions of the concave portion 2 c that contact theelectrode portion of the protective elements 5 are processed intolowered shape. In this case, as shown in FIG. 9, the protective elements5 are arranged to bridge the light-receiving side lead frame 2 b(concave portions 2 c). By providing such concave portions, it is notonly possible to ensure the electrical isolation distance between thelight-receiving element and the light-emitting element within thedevice, but it is also easy to position the protective elements 5 whenthey are mounted.

It should be noted that the arrangement of the protective element 5 andthe shape of the lead frames 2 a and 2 b are not limited to theabove-noted case shown in FIG. 6 and FIG. 7, and concave portions 2 conto which the protective elements 5 are mounted may also be formed onthe light-emitting side lead frame 2 a, for example.

Third Embodiment

Next, a third embodiment of the present invention is explained withreference to the drawings.

FIG. 10 and FIG. 11 show the third embodiment of the present invention.

In the solid state relay 1 according to this embodiment, it is possibleto suitably mount a plurality of protective elements of different sizesin the solid state relay 1 with a configuration according to the firstor second embodiment.

In the solid state relay 1 shown in FIG. 10, a floating island portion 2d and a peripheral portion 2 e surrounding this floating island portion2 d are provided on the light-receiving side lead frame 2 b, a pluralityof mounting portions 2 f with different gaps between the opposingfloating island portion 2 d and the peripheral portion 2 e are providedat the floating island portion 2 d and the peripheral portion oppositethe floating island portions 2 d, and the protective elements 5 aremounted to bridge the mounting portions 2 f.

Because the gaps (y1, y2, and y3) between the floating island portion 2d and the peripheral portion 2 e vary among the mounting portions 2 f inthis manner as shown in FIG. 11, it is possible to suitably mount theplurality of protective elements 5 of different size onto thecorresponding mounting portions 2 f.

As described above, the present invention can be applied to solid staterelays that simplify the assembly steps and make the devices smaller.

It should be noted that the invention may be embodied in other formswithout departing from the spirit or essential characteristics thereof.The embodiments disclosed in this application are to be considered inall respects as illustrative and not limiting. The scope of theinvention is indicated by the appended claims rather than by theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are intended to be embraced therein.

1. A solid state relay formed by mounting a light-emitting element on alight-emitting side lead frame, mounting a light-receiving element or alight-receiving element and a switching element which operates inresponse to signals from the light-receiving element on alight-receiving side lead frame, arranging the light-emitting side andthe light-receiving side lead frames in opposition to each other, andsealing the lead frames into one package, wherein a protective elementthat protects the light-emitting element or the light-receiving elementis mounted on at least one of the lead frames; and wherein theprotective element or the protective element and the switching elementare arranged inside a primary mold resin that seals the light-emittingelement and the light-receiving element.
 2. The solid state relayaccording to claim 1, wherein the protective element is arranged to beseparated from the opposing lead frame and any of the light-emittingelement, the light-receiving element, or the light-receiving element andthe switching element mounted on this lead frame.
 3. The solid staterelay according to claim 2, wherein the protective element is mountedopposite a region where the lead frame is not present.
 4. The solidstate relay according to claim 2, wherein the protective element ismounted on a side of at least one of the lead frames that is the rearside to the side on which elements are mounted.
 5. The solid state relayaccording to claim 2, wherein the lead frame opposite the protectiveelement is bent in the direction away from the protective element. 6.The solid state relay according to claim 2, wherein a concave portionfor mounting the protective element is formed in at least one of thelead frames.
 7. The solid state relay according to any of the claims 1to 6, wherein a floating island portion and a peripheral portionsurrounding this floating island portion are provided in at least one ofthe lead frames; wherein a plurality of mounting portions with differentgaps between the floating island portion and the peripheral portionopposing each other are provided at the floating island portion and theperipheral portion that opposes the floating island portion; and whereinthe protective elements are mounted to bridge these mounting portions.